The invention relates to a field device for automation systems of the type of the main claim.
In automation systems, field devices are used which serve for example to record process parameters and/or to influence regulation parameters and which are connected via one or more interfaces to other field devices or to higher planes of the automation system. Generally the field device comprises a unit for internal data organisation, one or more communication interfaces (1-n), one or more process interfaces (1-n), (0-n) man-machine interfaces, elements for signal processing and (0-n) persistent memories, the interfaces, the elements for signal processing and the persistent memory having access to data in the unit for internal data organisation. The expressions in brackets give the number of the respective elements, but obviously a field device can contain other constituent parts, such as power supply, mechanical elements and the like.
The unit for internal data organisation as well as the persistent memory contain the process image with process variables, configuration parameters for communication, the program or programs to be used, stored fixed values of the parameters used in the process image or the like. The process interfaces record the measured variables or respectively give the regulation parameters for the automation process; the elements for signal processing, which are configured for example as functional components, process the measured variables and/or regulation parameters, and the communication interfaces, which can be configured for bus systems, serve to communicate with other devices. The man-machine interfaces are realised for example by a local control display or a local input unit or by switches. The unit for internal data organisation and the persistent memory are formed by a microprocessor system. All the data-processing components of the field device, i.e. all the interfaces, and the signal processing work on the internal data organisation, i.e. they read and write the data stock there.
Field devices are used in all the fields of automation, e.g. process industries, such as the chemical industry, power stations or in manufacturing industries, such as vehicle construction. These devices are for example sensors (pressure, temperature, filling level, . . . ), actuators (valves, converters, motors, . . . ) and more.
As an example of a simple field device can be quoted a sensor for measuring concentrations which comprises a vibrating quartz crystal, an oscillator, a microprocessor system having memories and timing circuits and the like, as well as a serial interface and a power supply for all the elements. Here the vibrating quartz crystal represents the process interface; it detects additions of mass by the alteration of an oscillation frequency and converts it into an electrical signal. The signal processing is carried out via the oscillator and the microprocessor system, the latter also representing the internal data organisation and the persistent memory as well as, together with the serial interface, the communication interface. In the described example there is no man-machine interface. The vibrating quartz crystal detects the addition of mass and the concentration is determined, the concentration value being capable of being transmitted via the serial interface to other components of the automation system, or regulation parameters can be calculated in the concentration sensor itself and these parameters can be transmitted to actuators via the interface.
In principle, the data and functions of field devices in automation systems are used by other field devices or other automation components; these are e.g. installation tools, tools for service/maintenance, control systems, stored program controls, other field devices, ERP systems, MES systems and more (ERP—Enterprise Resource Planning; MES—Manufacturing Execution System).
When field devices are used there are a number of problems which are described below, the problems arising both through external users, i.e. through other components of the automation system, and through internal users. A user has access via the constituent parts of the field device to its internal data organisation. Internal users are the described constituent parts of the field device. External users are automation components or their constituent parts or other field devices or their constituent parts or constituent parts of the process in an automation system which are connected to the field device via the communication, process or man-machine interfaces. User access can be triggered by the automation system itself, by people using it or by the process to be automated.
Inconsistencies due to simultaneous reading/writing of a datum of the internal data organisation by a plurality of users, e.g.                more than one communication (e.g. Ethernet and any field bus),        cyclic and acyclic communication (e.g. in the PROFIBUS cyclic via C1 connection and acyclic via C2 connection)        local control display and communication via the communication interface,        any other combinations of the above-described data-processing components.        
Inconsistency due to reading/writing of logically associated data of the internal data organisation by one user in a plurality of steps (e.g. measured value plus status or lower and upper limit values or measured value and unit or set of parameters), e.g.                acyclic in a plurality of telegrams (e.g. Ethernet, PROFIBUS),        partially cyclic, partially acyclic (e.g. PROFIBUS).        
Lack of the possibility of producing a defined original state in carrying out a plurality of writing/reading operations in sequence, when the user requires this, e.g.:                reconfiguration,        downloads (e.g. from functional components or of all the parameters of the field device        uploads (e.g. of all the parameters of one or more field devices)        downloads into a plurality of field devices.        
Lack of consistency of the internal data organisation of a field device with                data organisations of other field devices        data organisations of automation components.        
When practical automation tasks are solved with the aid of field devices, the above-mentioned problems occur in any combinations. The solution for the described problems therefore becomes more urgent since field devices are no longer used only in isolation or connected for communication 1:1, but to an increasing extent permit communication with a plurality of users. The increasing integration into higher planes of automation technique (e.g. for asset management) contributes to this.